A variety of afflictions such as peripheral vascular disease, ischemic strokes, and various other infarctions such as myocardial infarctions, pulmonary infarctions, splenic infarctions, limb infarctions, and avascular necrosis of bone tissue, are associated with blockages of blood vessels in a human patient, usually due to thrombi (blood clots) or excessive plaque buildup. Because the tissues associated with a blood vessel typically rely upon that vessel for a continuous supply of oxygen and nutrients, a blockage of that vessel create stresses on these associated tissues, as well as the vascular tissues themselves. As a result, effective treatment of an affliction associated with a blockage of a blood vessel may be complicated by the response of the weakened vascular tissues to the restored blood flow, and the associated elevation of flow velocity and blood pressure. The treatment of ischemic strokes presents a particularly poignant example of the interplay of the condition of the vascular tissues and the outcome of a treatment.
Ischemic strokes, defined herein as the rapid loss of a brain function due to a sudden disruption of the brain's blood supply due to a blood clot, are a leading cause of death worldwide. Those fortunate enough to survive an ischemic stroke may still face significant losses of brain function such as loss of the ability to move one or more limbs on one side of the body, loss of the ability to understand or formulate speech, and/or an inability to see one side of the visual field. Current treatments for ischemic strokes must be completed within 3 to 6 hours of the stroke due to the associated weakening of the brain vascular tissues. Strokes associated with the disruption of flow within relatively large circulatory vessels must be treated quickly due to the larger area of the brain infracted, the resultant lower coverage of blood flow to the surrounding tissue from collateral vessels, as well as the potentially devastating and significant loss of function.
If the stroke is not treated within this relatively brief window of opportunity, removal of the clot to restore blood flow carries with it a significant risk of a secondary hemorrhagic event resulting in additional brain damage or death of the patient. As a result, a high proportion of physicians are relatively reluctant to remove blood clots outside of this treatment window, and patients are instead forced to cope with the functional deficits associated with the loss of brain function associated with the stroke event. Unfortunately, current treatment methods are unable to control the rate at which blood pressure and flow rate are restored to ischemic brain tissues and associated weakened blood vessels.
The use of current treatment methods are further limited by the inherent difficulty in pin-pointing the time at which a stroke occurred, as well as the challenge of transporting a patient to a facility capable of implementing one of these current treatment methods. For example, patients presenting with a stroke upon awakening from sleep are not strong candidates for current treatment methods due to the inability to identify the time of onset of the stroke. The time elapsed during a stroke event, the time taken to recognize that a stroke is occurring, the time taken to signal a need for assistance, the time taken for medical personnel to reach the patient, the time taken to transfer the patient to a treatment facility, and the time taken to diagnose the stroke condition all narrow the already-brief window of opportunity for treatment using existing methods. As a result, a significant number of patients are not viable candidates for treatment using existing methods.
There exists a need in the art for a device capable of controlling the flow rate and/or pressure within an afflicted vessel and/or a vessel associated with an afflicted tissue. A need in the art further exists for a method of treating an afflicted vessel and/or a vessel associated with an afflicted tissue using the device to vary the flow rate and/or pressure within the vessel as a treatment and/or in conjunction with an additional treatment.